Actuators are widely used throughout many industries to control the movement of various components. Some actuators are configured to transfer rotational energy between components to, ultimately, effectuate movement of a surface or component. Similarly, some actuators are configured to transfer linear energy between components to, ultimately, effectuate movement of a surface or component. Still further, some actuators are configured to transfer both rotational and linear energy between components to, ultimately, effectuate movement of a surface or component.
Some actuator applications require reliable, fail-free or fails-safe mechanical or electro-mechanical actuators. More specifically, many applications require actuators which include mechanisms that limit an input force and/or release the actuated load during fail situations, such as when one component of the actuation system in which the actuator is installed fails or is otherwise compromised and thereby limits or prevents movement of the actuated surface or component (i.e., the load recipient). Such mechanisms limit or prevent damage to components during overload situations and free the actuated load from a jam in the actuation system. For example, some actuation systems employ torque limiters or overload clutches which automatically limit torque throughput by slipping or shearing of components at a certain predefined maximum torque. Similarly, some actuators employ mechanisms which automatically limit axial force throughput by slipping or shearing of components at a certain predefined maximum axial force. However, these mechanisms are often unreliable, inaccurate, cannot be customized (as the “release” parameter often cannot be changed after installation), are difficult to reset after “release” and are difficult to scale. These mechanisms are also typically designed to only limit force in a particular direction (e.g., only limit torque or only limit axial force).
These types of mechanism are therefore not well suited for applications in which prevention of overload situations and release of the actuated surface or components during a jam is vital. For example, in the aviation industry, reliability of actuators relied upon for control of flight control surfaces is paramount. Due to the operating conditions of flight control surfaces, movement of flight control surfaces in aircraft is effectuated by redundant actuators. When one of these actuators fails, such as when a jam occurs, it is vitally important that the failed actuator does not prevent movement of the flight control surface to which the actuator is coupled. Typically, movement of a flight control surface directly results in movement of the components of the actuators configured to effectuate movement of the surface. Thus, if an actuator has failed in a manner such that the components of the actuator are locked with one another or are otherwise incapable of movement, the failed actuator effectively prevents movement of the control surface by the other properly-functioning redundant actuators or other actuator control mechanisms.
As a result, a need exists for reliable, accurate and scalable actuators that are capable of selectively coupling and decoupling components of the actuator in response to a jam or other failure of the actuator to disengage components of the actuator to free the actuated component or surface from the failed actuator. In such situations, a particular need exits for actuators which are capable of selectively fixing or locking components of the actuator (such as rotationally or angularly, longitudinally or axially, or both rotationally and longitudinally) when the actuator is properly functioning, and also reliably responsive to a failure of the actuator (e.g., a jam in the actuator) to disengage components of the actuator with respect to one another (such as rotationally, longitudinally, or both rotationally and longitudinally) and, thereby, free the actuated component or surface (i.e., the load recipient).